Alkylation of paraffin hydrocarbons



Dec. 3l, 1957 J. E. GANTT ALKYLATION 0F PARAF'FIN HYDROCRBONS Filed May 14, 1956 3 Sheets-Sheet 1 Tmiamm,

Dec. 31, 1957 J. E. GANTT AmYLATIoN oF PARAFFIN HYDROCARBONS 3 Sheets-Sheet 2 Filed May 14, 1956 Dec. 31, 1957 J. E. GANTT ALKYLATION oF PARAFFIN HYDRocARBoNs Filed May 14, 1956 3 Sheets-Sheet 3 NGN I/VVENTOR James E. Gan/f vbwvh fsw www. www

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nited States Patent 'i ALKYLA'rIoN oF PARAFFIN HYDRoCARBoNS James E. Gantt, Elmwood Park, Ill., assignor to Universal Oil Products Company, Des Plaines, lll., a corporation of Delaware Application May 14, 1956, Serial No. 584,685

3 Claims. (Cl. 260-683.4)

This invention relates to the alkylation of hydrocarbons in the presence of an alkylation catalyst. More particularly, this invention relates to the alkylation of hydrocarbons in the presence of an acidic alkylation catalyst. Still more particularly, this invention relates to the alkylation of hydrocarbons in the presence of a hydrogen fluoride catalyst.

This invention is particularly concerned with an improved process for the production of higher molecular weight isoparains by the alkylation of lower boiling isoparatins with olens in the presence of an acidic alkylation catalyst, such as hydrogen fluoride, in which process maximum utilization is made of available low boiling isoparaiiin with minimum loss thereof. Simultaneously with the maximum utilization of available low boiling isoparaflin, this invention relates to control of concentration of low boiling isoparaflins within a preferred range in order to obtain optimum product quality. These objectives are accomplished by the unique combination of the present invention as will be set forth hereinafter.

Production of higher molecular weight isoparaiiins having valuable antiknock properties and, therefore, suitable for use in automotive and aviation fuels, is of considerable importance n the petroleum refining industry. Furthermore, the recent introduction of automobiles engines of high compression ratio has necessitated the utilization of high antiknock fuels in these engines to obtain maximum horsepower output therefrom. Thus, the demand for higher and higher octane number fuels has led to increased use of higher molecular weight isoparaiiins as blending agents in gasolines. A convenient source of such higher molecular weight isoparatlns is the catalytic alkylation of low boiling isoparaflns such as isobutane, with olelins such as propylene, the butylenes, and the amylenes. It is a further object of this invention to provide a process which will yield such high octane motor fuels.

Alkylation of isoparains utilizing liquid catalyst such as hydrogen fluoride or sulfuric acid has ordinarily been conducted by introducing the hydrocarbon charging stock and a catalyst into a reaction zone. The hydrocarbon catalyst mixture has been then and there maintained at the desired temperature, pressure, and for the desired time of contact, and it has been preferable that a substantial molar excess of isoparallins over olelins be maintained throughout the entire reaction period. The reaction mixture has been withdrawn and introduced into a settling zone which ordinarily comprises a settler. The lower used catalyst layer has been recycled from the settler to the reaction zone, a portion thereof being preferably withdrawn from the system and introduced into a catalyst regeneration zone. The upper hydrocarbon layer from the settler has preferably been thoroughly subjected to precise fractionation for the recovery of gasoline boiling range products and for the separation of unconverted isoparains which may be recycled to the reaction zone. Such a fractionation zone has been operated usually under a 3:1 or higher reux and the recovered isoparaliin therefrom recycled to the reaction zone. Such precise fraction- Patented Dec. 31, 1957 ICC ation is expensive in heat requirement. The bottoms from such a fractionation zone have been again fractionated for the removal of n-paraiiin therefrom and the recovery of gasoline boiling range hydrocarbons. By the use of the process of the present invention, fractionation for recovery of isoparaflin is accomplished with minimum heat requirement in the absence of external reflux and isoparain which in an ordinary alkylation process is lost in the normal parallin fractionation zone overhead stream is recovered. These and other objectives can be accomplished by utilization of the novel combination process of the present invention.

One embodiment of this invention relates to a process for producing a high antiknock hydrocarbon fraction by reacting an isoparalin and an olefin in the presence of an alkylation catalyst which comprises fractionating a mixed n-paraflin-isoparatlin stream and an isoparainlean parain fraction produced as hereinafter described in a fractionation zone to produce a substantially normal paraflin-free isoparaiiin overhead fraction and a substantially isoparain-free normal parain bottoms fraction, contacting said isoparain fraction with an isoparain-rich parain recycle fraction produced as hereinafter described and an olefin in a reaction zone in liquid phase in the presence of an alkylation catalyst, separating from eluents of said reaction zone a liquid phase comprising primarily alkylation catalyst and a liquid hydrocarbon phase comprising a large excess of unreacted isoparaflin, n-parafn, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating an isoparalin-rich paraffin fraction overhead therefrom, recycling said isoparafn-rich paratlin fraction to the reaction zone as aforesaid, separating an isoparatiin-lean normal-paraiin and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating an isoparain-lean low boiling paran fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isoparaflin-lean low boiling parain fraction to said first-mentioned fractionation zone for the recovery of isoparain therefrom.

Another embodiment of this invention relates to a process for producing a high antiknock hydrocarbon fraction by reacting isobutane and an olefin in the presence of an alkylation catalyst which comprises fractionating a mixed n-butane-isobuta-ne stream and an isobutane-lean normal-butane fraction produced as hereinafter described in a fractionation zone to produce a substantially n-butane-free isobutane overhead fraction and a substantially isobutane-free n-butane bottoms fraction, contacting said isobutane fraction with an isobutane-rich parafiin recycle fraction produced as hereinafter described and an olefin in a reaction zone in liquid phase in the presence of an alkylation catalyst, separating from efuents of said reaction zone a liquid phase comprising primarily alkylation catalyst and a liquid hydrocarbon phase comprising a large excess of unreacted isobutane, n-butane, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating an isobutane-rich paraffin fraction overhead therefrom, recycling said isobutane-rich parain fraction to the reaction zone as aforesaid, separating an isobutane-lean n-butane and higher boiling hydrocarbon stream from the bottoms of said stripping means, passing said last-mentioned stream to a fractionation zone, separating an isobutane-lean n-butane fraction'overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isobutane-lean n-butane fraction to the first-mentioned fractionation zone for the recovery of isobutane therefrom.

One specific embodiment of this invention relates to a process for producing a high antiknock hydrocarbon fraction by reacting isobutane and an olefin in the presence of a liquid hydrofluoric acid catalyst which comprises fractionating a mixed n-butane-isobutane stream and an isobutane-lean n-butane fraction produced as hereinafter described in a fractionation zone to produce a substantially n-butane-free isobutane overhead fraction and a substantially isobutane-free n butane bottoms fraction, contacting said isobutane fraction with a isobutanerich parafiin recycle fraction produced as hereinafter described and an olefin in a reaction zone in liquid phase in the presence of liquid hydrofluoric acid, separating from effluents of said reaction zone a liquid phase comprising primarily hydrofluoric acid and a liquid hydrocarbon phase comprising a large excess of unreacted isobutane, n-butane, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating an isobutane-rich parafn fraction overhead therefrom, recycling lsaid isobutane-rich paraffin fraction to the reaction zone as aforesaid, separating an isobutane-lean n-butane and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating an isobutane-lean n-butane fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isobutane-lean n-butane fraction to the first-mentioned fractionation zone for the recovery of isobutane therefrom.

Another specific embodiment of this invention relates to the process for producing a high antiknock hydrocarbon fraction by reacting isobutane and an olefin in the presence of a sulfuric acid alkylation catalyst which comprises fractionating a mixed n-butane-isobutane stream and an isobutane-lean n-butane fraction produced as hereinafter described in a fractionation zone to produce a substantially n-butane-free isobutane overhead fraction and a substantially isobutane-free n-butane bottoms fraction, contacting said isobutane fraction with an isobutane-rich paratiin recycle fraction produced as hereinafter described and an olefin in a reaction zone in liquid phase in the presence of a `sulfuric acid alkylation catalyst, separating from efliuents of said reaction zone a liquid phase comprising primarily sulfuric acid and a liquid hydrocarbon phase comprising a large excess of unreacted isobutane, n-butane, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating an isobutane-rich paraffin fraction overhead therefrom, recycling said isobutane-rich paraffin fraction to the reaction zone as aforesaid, separating an isobutane-lean n-butane and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating an isobutane-lean n-butane fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isobutane-lean n-butane fraction to said first-mentioned fractionation zone for the recovery of isoparafiin therefrom.

These embodiments, along with other features of the present invention will be described hereinafter in detail and in reference to the attached drawings. However, no intention to limit the generally broad scope of the present invention is meant to be inferred therefrom.

It is emphasized moreover that the present invention hereinafter described in detail in relation to hydrolluoric acid is not to be limited thereby. Other alkylating catalysts, especially other acid alkylating catalysts, are within the scope of the present invention and include sulfuric acid, phosphoric acid, Friedel-Crafts metal halides such as aluminum chloride, aluminum bromide, zinc chloride, and mixtures of these metal halides with a hydrogen halide. Another alkylating catalyst within the scope of the present invention is a mixture of boron trifluoride and hydrogen fluoride. While the specific operating conditions and concentrations in which these various alkylating catalysts are to be used will vary from one to another, in each case the operating condition will be selected so that the reaction will be conducted in the liquid phase under specific conditions such that the isoparaffin is alkylated by the olefin or olefins present therewith.

Previous processes for the alkylation of isoparatlins with olefins to produce a high antiknock motor fuel have all included precise fractionation means to separate the excess unreacted isobutane from the higher boiling hydrocarbons withdrawn from the reaction zone. Such precise fractionation means are expensive to build and to operate. Thus, these fractionation means are usually designed with maximum economy in mind, and therefore somepisobutane is withdrawn from the bottoms thereof along with n-butane and higher boiling hydrocarbons including the desired alkylate. Such withdrawn streams have then been passed to another fractionation means for the separation of low boiling hydrocarbons present therein from the alkylate. The overheads from these last-mentioned `fractionation means, usually called debutanizers, contain some isobutane and have been used mainly for motor fuel blending to meet vapor pressure requirements. Thus, isobutane loss from alkylation is dependent upon design and operation of the deisobutanizer, as hereinabove described. It is a feature of the present invention that such isobutane loss as hereinbefore experienced commercially is substantially eliminated along with the necessity for precise fractionation as has heretofore been necessary in fractionation zones referred to as deisobutanizers. Commercially, fractionators such as deiso butanizers are large in size and expensive in design, construction and operation. In the operation of such a fractionator, the hydrocarbons withdrawn from the reaction zone, including isobutane, are introduced to the deisobutanizer at about the center or upper section thereof so that the desired separation by fractionation is thereby effected. For example, in a commercial deisobutanizer 9 feet in diameter and 110 feet high containing 50 trays spaced 24" apart, the hydrocarbon feed is distributed onto tray 12, numbering from the top, and the isobutane separated overhead therefrom. This separation in these deisobutanizers is accomplished by an external reflux of isobutane. This external reflux of isobutane is normally added to tray No. l. Further, this isobutane reflux is normally in the amount of at least 3 mols of freshly separated isobutane per mol of isobutane recycled, although somewhat lower and higher reflux ratios may be used. The use of such reflux ratios in cost terms means that enough heat must be supplied to the bottom of the deisobutanizer to vaporize four mols of isobutane while recovering just one mol of isobutane for recycle purposes in the process. Prior to my invention, it has been considered necessary in order to obtain the desired purity isobutane for recycle purposes and to minimize isobutane loss from the process to operate by means of such a deisobutanizer or other fractionation column, for removal of isoparans and recycle thereof. This desired purity of isobutane is necessary for recycle purposes so that the ratio of isobutane to n-butane in the feed to the reaction zone and the ratio of isobutane to olefin in the same feed will be such that the desired alkylation of the isobutane with the olefin will take place. Furthermore, such precise fractionation was also considered necessary to insure minimum isobutane loss in the deisobutanizer bottoms. Such loss is now overcome by the process of my invention wherein some isobutane is allowed to remain in the stripper bottoms and this isobutane is recovered overhead from the debutanizer and this overhead stream is recycled to a feed preparation deisobutanizer for recovery therefrom.

While operating in accordance with my invention, the need for such a product deisobutanizer is eliminated while still maintaining the desired purity of isobutane which is recycled back to the reaction zone and at the same time minimizing isobutane loss from the process. These desired features are accomplished by a stripper which will hereinafter be referred to as an isostripper, and by the use of which, isobutane of the desired purity for recycling is obtained with approximately one-half of the necessary heat input which is ordinarily necessary when operating with a deisobutanizer. For example, when operating with a deisobutanizer, and with an isobutane to olefin ratio of 6:1 in the combined feed to the reaction zone, it is necessary to vaporize 24 mols of isobutane in the deisobutanizer per 6 mols of isobutane available as recycle isoparaffin. Furthermore, it is sometimes desirable when operating to produce a higher antiknock fuel such as for use in aviation gasoline, to increase the ratio of isobutane to olefin in the hydrocarbon feed to the reaction zone to higher values, such as 10:1 or 20:1 or higher. It is readily apparent that when such an operation becomes desirable, the load on the deisobutanizer is increased multifold. I have discovered that this difficulty can be overcome with a simultaneous reduction in size of the fractionation column known as the deisobutanizer by replacement of said deisobutanizer with an isostripper of the present invention. For example, when operating with fan isostripper, and an isobutane to olefin ratio of 12:1 in the hydrocarbon feed to the reaction zone, the size of the isostripper is approximately one-half of the size which would be necessary for a typical deisobutanizer operating in a process maintained at a 6:1 isobutane to olefin ratio. Furthermore, the heat input to the isostripper is approximately one-half of that necessary when operating with a deisobutanizer, and a desired purity of isobutane overhead is maintained so that the desired isobutane to n-butane ratio in the hydrocarbon feed to the reaction zone is as desired. This is accomplished by introducing the cold hydrocarbon stream from the settler, and having a high isobutane. content to the top tray or trays of the isostripper and in the absence of any substantial amount of external reux of outside isobutane. That operation in accordance with the process of the present invention will effect a considerable saving commercially is readily apparent to one skilled in the art.

The accompanying diagrammatic drawings illustrate specific process flows embodying the features as hereinbefore set forth.

Referring to Figure I, an isobutane-n-butane stream comprising, for example, field butanes, is passed as a liquid under pressure through line 1, from charge pump 2 to lines 3 and 4 into an upper portion of deisobutanizer 5. The isobutane-n-butane stream is combined in line 4 with a recycled isobutane-lean n-butane stream from line 52 as hereinafter set forth. The combined charge to deisobutanizer 5 is fractionated therein and a substantially n-butane-free isobutane stream is separated overhead therefrom. This substantially n-butane free isobutane stream passes from deisobutanizer 5 overhead through line 6, is condensed in condenser 7 and is passed through line 8 into deisobutanizer receiver 9. From deisobutanizer receiver 9, the substantially n-butane free isobutane passes through line 10 to pump 11 and into line 12 which provides isobutane reux for feed deisobutanizer 5, and in addition, directs the requisite quantity of substantially n-butane free isobutane through line 14 to lines 18, 19, and 20 as hereinafter described. An olefin-containing stream as a liquid under pressure is passed through line 15, from pump 16 into line 17 and line 18 for combination with the feed isobutane as hereinabove described. This isobutane-olefin feed is passed to line 19 and joined therein with an isobutane-rich paraffin recycle stream from line 38. The combined feed is passed from line 19 to line 20 where it is joined by recycle acid catalyst from line 27 and the combined feed and recycle acid catalyst are then passed to contactor 21. Generally, some means of removing the heat of reaction from con- '.tactor zone 21 is provided, such as, an internal cooler or heat exchanger not shown.l The mixture ofhydro-V carbons and acid catalyst carried over therewith is withdrawn from contactor 21 through line 22 to alkylation settler 23, wherein acid catalyst settles out in the lower layer and is withdrawn through line 24 as shown. The catalyst layer then passes through line 28 to an acid regeneration zone and after regeneration back through line 29, line 25, pump 26 and line 27 to the contactor zone 21. When regeneration is not utilized the acid withdrawn through line 24 passes through line 25, pump 26, lines 27 and 20 back to contactor zone 21. When fresh acid is desired, this acid is introduced through line 29 to line 25 and passes to the contactor as hereinabove described. Addition of the acid at this point avoids contacting concentrated acid with olefins in the feed and the danger of olefin polymerization is thus minimized.

The hydrocarbon products containing a relatively small amount of dissolved acid alkylation catalyst are withdrawn from settler 23 through line 30 and are introduced to the isostripper 31. This introduction is made to the top tray of the isostripper. Within this isostripper a substantial separation is made between the lower boiling isobutane and the higher boiling n-butane and reaction products. The isobutane is removed overhead from the isostripper through line 32, condensed in condenser 33, and passed through line 34 to the isostripper receiver 35. When the acid catalyst utilized is hydrogen uoride, this overhead isobutane rich paraffin recycle fraction also contains essentially all of the hydrogen uoride which was dissolved in the hydrocarbon layer as hereinbefore described. The isobutane-rich paraffin is withdrawn from settler 35 through line 36 by recycle pump 37 and is passed through line 38 which recycles the isobutane back through line 19 as hereinbefore set forth. The isostripper is heated by reboiling a portion of the higher boiling hydrocarbons which are withdrawn from the bottom of the isostripper through line 39 to reboiler 40. A reboiler may be gas fired or heated by steam or by any other suitable means. The thus heated heavier hydrocarbons are then passed through line 41 back to the bottom of isostripper wherein heat is imparted to said isostripper. The heavier hydrocarbons containing some isobutane which has not been removed overhead, n-butane,

and the reaction products are withdrawn through line 42 and discharged therefrom into debutanizer 43. Within this debutanizer separation is made between the C4 parafiins and the reaction products. The C4 paraiiins are removed overhead from the debutanizer through line 44, condenser 45, and passed through line 46 to debutanizer receiver 47. This isobutane lean paraffin fraction is then withdrawn from the debutanizer receiver 47 through line 4S and charged by pump 49 to line 50 connected with lines 51 and 52. Line 51 provides reflux for the debutanizer to insure the precise degree of fractionation necessary therein. The net overhead from the debutanizer thus passes through line 52 back to line 4 as hereinbefore described for recovery of isobutane therefrom in deisobutanizer 5. Deisobutanizer 5 is heated by reboiling a portion of the n-butane bottoms which are Withdrawn from the bottom of deisobutanizer 5 through line 57 to the reboiler 58. Again, this reboiler may be gas fired or heated by steam or any other suitable means. The thus-heated n-butane is then passed through line 59 back to the bottom of deisobutanizer 5 wherein heat is imparted therein. A portion of the bottoms containing the undesirable through line 60, cooled in heat exchanger 61 and withdrawn from the process through line 62. Line 62 may direct the normal butane to gasoline blending or to an independent isomerization process wherein the n-butane may be converted to isobutane for further use in the process.

Debutanizer 43 as hereinabove described is heated by withdrawing a portion of the bottoms through line 53 to reboiler 54. Heat is imparted to the heavy hydrocarbons in reboiler 54 and the heavy hydrocarbons are n-butane is withdrawn from reboiler 58 7 then passed through line 55 back to the bottom of debutanizer 43. The net make of alkylate is withdrawn from the process through line 56 for necessary fractionation to separate a narrow boiling or wide boiling range alkylate fraction therefrom. The means for such fractionation are not shown.

The alkylation of isoparains with oletins in the presence of a hydrogen fluoride catalyst may be conducted at a temperature of from about F. to about 200 F. although the temperature of reaction is preferably within the range of from about 50 F. to about 150 F. By the term hydrogen fluoride catalyst as used throughout this specification and appended claims, it is intended to include catalysts wherein hydrogen fluoride is the essential active ingredient. Thus, it is within the scope of my invention to employ substantially anhydrous hydrogen fluoride or hydrouoric acid or hydrogen fluoride containing various additives or promoters or boron trifluoride. Ordinarily, commercial anhydrous hydrogen uoride will be charged to the alkylation system as fresh catalyst. However, it is possible to use hydrogen fluoride containing as much as about 10% water or more. Excessive dilution with water is generally undesirable since it tends to reduce the alkylating activity of the catalyst and introduces corrosion problems. The pressure on the alkylation system is ordinarily just high enough to maintain the hydrocarbons and catalyst in substantially liquid phase, that is, from about 50 to about 250 pounds per square inch. The time factor in the alkylation process is conveniently expressed in terms of space time which is defined as the volume of catalyst within the contacting zone divided by the volume rate per minute of hydrocarbon reactants charged to the zone. Usually the space time will fall within the range of from about 5 to about minutes although in certain cases it may be desirable to extend this range in either direction. It is preferable to maintain at all times a substantial molar excess of isoparaiiins to oleins in the hydrocarbon feed to the reaction zone, that is, from about 4:1 to about 20:1 mol ratio or higher. It is also preferable to maintain at all times a fairly substantial molar excess of isoparafiins over n-paraflins in the hydrocarbon feed to the alkylation zone, that is, from about 3:1 to about 8:1 or higher. It is in this latter function that the advantages of an isostripper over a deisobutanizer stand out. In general, the volumetric ratio of catalyst to hydrocarbon in the contacting zone should be about 2:1 to about 3 :l while ratios of from about 0.5:1 to about 5:1 will give satisfactory results.

Although the alkylation process of the present invention is particularly advantageous in the case of alkylation of isobutane with normally gaseous olefins such as butylenes, it is generally applicable to the alkylation of any branched chain parainic hydrocarbon containing at least one tertiary carbon atom per molecule with an olenic hydrocarbon. As olefinic reactants, the normally gaseous olefins including ethylene, propylene, 1butcne, Z-butene, isobutylene, and the various isomeric amylenes may be employed. In the case of the less reactive ethylene, it is generally desirable to have boron triuoride present in the catalyst in addition to hydrogen fluoride, or to use sulfuric acid or aluminum chloride as the catalyst. Normally liquid olefins such as armylenes, hexenes, etc., including polymers of the lower molecular weight normally gaseous oleiins may also be employed as olefinic reactants in the process with good results.

A specific example of the operation of the process with hydrogen fluoride as the alkylation catalyst and as the process is carried out similar to that set forth hereinabove with reference to Figure I is described herewith now in connection with Figure II.

This example illustrates the alkylation of isobutane with C4 olefins. The isobutane is obtained by precise fractionation of eld butanes. The C4 olefins are obtained from a fluid catalytic cracking unit gas concentration plant and consist of the debutanizer overhead from this plant. Reaction conditions include F. in the contacting zone, and isobutane to olefin mol ratio of 6.0:1, and an isobutane content of greater than 62 mol percent in the contacting zone effluent.

Referring to Figure II, an isobutane-n-butane stream comprising field butanes in the quantity of 1058 barrels per day is passed as a liquid under pressure through line 101, and is pumped by charge pump 102 through lines 103 and 104 to an upper portion of feed deisobutanizer 105. These eld butanes have a composition as follows: 1.0 mol percent propane, 45.0 mol percent isobutane, and 54.0 mol percent n-butane. The feed deisobutanizer is a fractionation tower with an inside diameter of 41/2 feet, a height of 130 feet, containing 60 trays spaced 24 inches apart. This fractionation zone operates at 115 p. s. i. g. with a top temperature of 138 F., a bottom temperature of 160 F., and a 3.5 :l reux ratio. The above described isobutane-n-butane stream has combined therewith in line 104, 587 barrels per day of recycle isobutane-lean n-butane from line 173 as hereinafter described. This recycle isobutane-lean n-butane stream consisting of the debutanizer overhead contains 25.9 mol percent isobutane, 73.5 mol percent n-butane, and 0.67 mol percent pentanes. Thus the total combined feed to deisobutanizer 105 amounts to 1645 barrels per day and has a composition as follows: 0.6 mol percent propane, 38.2 mol percent isobutane, 61.0 mol percent n-butane, and 0.2 mol percent pentanes. The combined feed to deisobutanizer 105 is fractionated therein under a 3.5:1 reflux ratio and a substantially n-butane-free isobutane stream is separated overhead therefrom in an amount of 629 barrels per day. This 629 barrels per day containing 1.7 mol percent propane, 93.3 mol percent isobutane, and 5.0 mol percent n-butane is withdrawn from deisobutanizer 105 overhead through line 106 and is condensed in condenser 107 and passes through line 108 to deisobutanizer receiver 109. The liquid is withdrawn from the receiver through line 110, is pumped by pump 111 through line 112 to reflux line 113 and depropanizer feed line 114.

An olefin-containing stream from gas concentration unit debutanizer overhead (comprising low boiling hydrocarbons produced by a uid catalytic cracking unit) is passed as a liquid under pressure through line 115 and pumped by pump 116 through line 117, condenser 118, and line 119 to depropanizer 120. This olefin-containing stream has a composition as follows: 0.4 mol percent ethane, 22.5 mol percent propylene, 16.4 mol percent propane, 29.1 mol percent butencs, 16.7 mol percent isobutane, 14.2 mol percent n-butane, 0.3 mol percent pentenes, and 0.4 mol percent pentanes; and is fed to the depropanizer in the quantity of 2849 barrels per day. It is joined in line 117 with 673 barrels per day of an isobutane drag stream from line 162 consisting of 3.0 mol percent propane, 76.6 mol percent isobutane, 19.2 mol percent nbutane, 0.5 mol percent pentanes, and 0.7 mol percent light alkylate. The depropanizer serves two functions. By recycle of the isobutane drag stream through line 162 to the depropanizer, the propane made during hydrogen transfer reactions in the alkylation process and that contained in fresh feed is removed from the process and propane buildup therein is thus prevented. Also, the depropanizer serves as a feed preparation fractionation zone for separating C3 hydrocarbons from higher boiling low boiling hydrocarbons which C3 hydrocarbons can be sent to a polymerization unit for the preparation of motor fuel blending components therefrom. Depropanizer 120 is a fractionation column four and one-half feet in diameter, 70 feet high containing 30 trays spaced 24 inches apart. It operates at 275 p. s. i. g. with a top temperature of F., a bottom temperature of 220 F., and a reflux to feed ratio of 121:1. The total combined depropaniier feed from line 114 as hereinabove described in the quantity of 629 barrels per day, from line 115 in the quantity of 2849 barrels per day, and from line 162 in the quantity of 673 barrels per day has a composition as follows: 0.3 mol percent ethane, 15.7 mol percent propylene, 12.3 mol percent propane, 20.6 mol percent butenes, 36.6 mol percent isobutane, 13.7 mol percent n-butane, 0.3 mol percent pentanes, and 0.1 mol percent light alkylate. After fractionation of the combined feed, the depropanizer overhead is passed through line 121, condenser 122 and line 123 to depropanizer receiver 124. The liquid hydrocarbons are withdrawn therefrom in line 125 by pump 126 which discharges into line 127 for reflux through line 128 and net depropanizer overhead withdrawal of 1017 barrels per day through line 129. The net depropanizer overhead withdrawal through line 129 in the quantity of 1017 barrels per day has a composition as follows: 1.0 mol percent ethane, 55.2 mol percent propylene, 42.4 mol percent propane, 0.4 mol percent butenes, 0.7 mol percent isobutane, and 0.20 mol percent n-butane. As hereinabove stated this depropanizer overhead stream is a suitable feed stock for catalytic polymerization for the production of high antiknock motor fuel blending components.

The depropanizer is heated by reboiling a portion of the higher boiling hydrocarbons which are withdrawn from the bottom of the depropanizer through line 130 to reboiler 131. The heated heavier hydrocarbons are then passed through line 132 back to the bottom of the depropanizer wherein heat is imparted to the depropanizer. The heavier hydrocarbons comprising the net contactor feed are withdrawn from the depropanizer through line 133, cooled in condenser 134 and passed through lines 135, 136 and 137 to contactor 133. This net feed in the amount of 3134 barrels per day has a composition as follows: 0.3 mol percent propylene, 0.6 mol percent propane, 28.5 mol percent butenes, 50.5 mol percent isobutane, 18.9 mol percent n-butane, 0.4 mol percent pentenes, 0.5 mol percent pentanes, and 0.2 mol percent light alkylate. This net contactor feed is combined in line 136 with recycle isobutane from the isostripper hereinafter described, said recycle isobutane being passed to line 136 via line 149. This recycle isobutane is supplied in the quantity of 5255 barrels per day and has a composition as follows: 3.0 mol percent propane, 76.7 mol percent isobutane, 19.1 mol percent n-butane, 0.5 mol percent pentanes, and 0.7 mol percent light alkylate. The combination of the recycle isobutane from line 149 with the depropanizer bottoms from line 135 results in a combined contactor feed stream of 8389 barrels per day having a combined composition as follows: 0.1 mol percent propylene, 2.1 mol percent propane, 10.8 mol percent butenes, 66.6 mol percent isobutane, 19.0 mol percent nbutane, 0.2 mol percent pentenes, 0.5 mol percent pentanes, and 0.5 mol percent light alkylate. Recycle or regenerated acid joins this combined feed stream from line 192 at line 137 and passes therewith to contactor 138. Contactar 138 containing liquid hydrouoric acid is maintained at 100 F. and alkylation of isobutanes in the combined feed stream with the butenes also contained therein takes place. The heat of reaction is removed from contactor 138 by means not shown. The mixture of hydrocarbons and acid catalyst carried over therewith is then withdrawn from contactor 138 through line 139 to alkylation settler 140. The total eluent from contactor 138 amounts to 8077 barrels per day and has a composition as follows: 2.6 mol percent propane, 62.0 mol percent isobutane, 21.4 mol percent n-butane, 1.3 mol percent pentanes, 12.2 mol percent light alkylate, and 0.4 mol percent heavy alkylate.

The hydrocarbon effluent as described hereinabove containing a relatively small amount of dissolved hydrogen fluoride is Withdrawn from settler 140 through line 141 and introduced to the isostripper 142. This introduction is made to the top tray of the isostripper. The isostripper is a fractionation column feet in diameter, 90 feet high, containing 40 trays spaced 24 inches apart. It operates at a pressure of p. s. i. g. with a top temperature of F., and a bottoms temperature of 265 F. It operates without external redux. Within this isostripper 142 a substantial separation is made between the lower boiling isobutane and higher boiling n-butane and reaction products. The isostripper overhead is withdrawn through line 143 cooled in condenser 144, and passes through line 145 to the isostripper overhead receiver 146. This isostripper overhead stream in the amount of 5928 barrels per day has a composition as follows: 3.0 mol percent propane, 76.7 mol percent isobutane, 19.1 mol percent n-butane, 0.5 mol percent pentanes, and 0.7 mol percent light alkylate. From the isostripper overhead receiver is withdrawn 5255 barrels per day of net recycle through line 147 by pump 148 which discharges to line 149 to line 136 as hereinbefore described. The composition of this net recycle stream is set forth hereinabove. A drag stream comprising 673 barrels per day is withdrawn from the isostripper overhead receiver 146 for HF stripping and propane removal from the system. This drag stream, which has the same composition as the recycle stream, is Withdrawn from isostripper overhead receiver 146 through line 155 by pump 156 which discharges into line 157 to HF stripper 158. The HF stripper is a fractionation zone two feet in diameter and 38 feet high containing 20 trays spaced 18 inches apart. The drag stream is charged onto tray No. 1 numbering from the top. The hydrogen uoride separated from the drag stream is withdrawn overhead through line 159 and recombines with line 143 as hereinabove described. The hydrocarbon portion of the drag stream is withdrawn from the HF stripper through line 160 via pump 161 which discharges into line 162. The recycle drag stream from line 162 is combined in line 117 with the gas concentration unit debutanizer overhead as aforesaid for propane removal therefrom.

The isostripper is heated by reboiling a portion of the higher boiling hydrocarbons which are withdrawn from the bottom of the isostripper through line 150 to reboiler 151. The heated heavier hydrocarbons are then passed through line 152 back to the bottom of the isostripper wherein heat is imparted to said isostripper. The heavier hydrocarbons containing some isobutane which has not been removed overhead, n-butane, and the reaction products are withdrawn through line 153 and passed through deiluorination zone 154. This deuorination zone 154 may consist of one or more towers filled with alumina, bauxite, aluminum rings, etc., for removal of the fluorides in the feed thereto. It is usually operated at a pressure of from about 150 p. s. i. g. and a temperature of about 265 F. While the fluorides in the feed are low, about 0.01 weight percent, it is desirable to remove them so that they will not decompose in later fractionation zones with production of hydrogen fluoride which is corrosive. The isostripper bottoms stream amounts to 2,149 barrels per day and has a composition as follows: 9.5 mol percent isobutane, 30.2 mol percent n-butane, 4.3 mol percent pentanes, 54.4 mol percent light alkylate, and 1.7 mol percent heavy alkylate. After deuorination in defluorination zone 154, this hydrocarbon stream passes through line 163 to debutanizer 164.

The debutanizer is a fractionation zone 3 feet in diameter and 70 feet high containing 30 trays spaced 24 inches apart. It is operated at 90 p. s. i. g. with an overhead temperature of 145 F. and a bottom temperature of 330 F. using a reflux to feed ratio of 0.75:1. The overhead from debutanizer 164 passes through line 165, is connected in condenser 166 and passes through line 167 to debutanizer overhead receiver 168. The liquid hydrocarbon debutanizer overhead is withdrawn from debutanizer overhead receiver 168 through line 169 by pump 170 which discharges into line 171 connected to line 172 for reflux and line 173 for recycle of the net overhead to the feed deisobutanizer via line 104 as hereinbefore described. The net debutanizer overhead in an amount of 587 barrels per day has the following composition: 25.9 mol percent isobutane, 73.5 mol percent nbutane, and 0.6 mol percent pentanes. By means of this recycle, isobutane loss from the system is minimized or prevented. The debutanzer is heated by reboiling a portion of the high boiling hydrocarbons which are withdrawn from the bottom of the debutanzer through line 174 to rcboiler 175. The heated heavier hydrocarbons are then passed through line 176 back to the bottom of debutanzer 164 wherein heat is imparted to said debutanizer. The net alkylate product is withdrawn from the bottom of the debutanzer through line 177 containing cooler 178 and is passed through line 179 to further fractionation means not shown. This net alkylate stream is in the amount of 1562 barrels per day and the stream withdrawn through line 179 has a composition as follows: 5.0 mol percent n-butane, 6.5 mol percent pentanes, 86.0 mol percent light alkylate and 2.7 mol percent heavy alkylate. The F-l clear octane number of this light alkylate is 93.0-94.0.

As hereinabove set forth, the debutanzer overhead is recycled to the feed preparation desobutanizer for recovery of isobutane. This feed desobutanizer 105 is heated by reboiling a portion of the higher boiling hydrocarbons, namely, n-butane, which is withdrawn from the bottom of the desobutanizer through line 180 to reboiler 181. The heated higher boiling hydrocarbons are then passed through line 182 back to the bottom of the desobutanizer 105 wherein heat is imparted to said desobutanizer. The higher boiling hydrocarbon, namely, n-butane, is withdrawn from the desobutanizer through line 183, cooled in cooler 184, and withdrawn from the system through line 185. This stream amounts to 1016 barrels per day and has a composition as follows: 5.0 mol percent isobutane, 94.7 mol percent n-butane, and 0.3 mol percent pentanes. This stream is conveniently utilized for motor fuel blending to obtain desired vapor pressure or, if desired, may be passed to an isomerization process wherein the n-butane is converted to isobutane for reuse in the alkylation process.

Hydrogen fluoride regeneration facilitates are also shown in the attached Figure II. Hydrogen fluoride which is carried over from contactor 138 is settled from the hydrocarbons in settler 140 as hereinabove described. This hydrogen uoride layer is withdrawn from the settler through lines 186, 187, and 188 to hydrogen fluoride charge drum 189. Hydrogen uoride is withdrawn from drum 189 through line 190 by pump 191 and recycled thereby through line 192 and 137 back to the contactor. Alternatively, all or a portion of the settled hydrogen fluoride may be withdrawn from settler 140 through lines 186 and 193 to the hydrogen fluoride regeneration zone 198. A portion of the hydrogen fluoride from line 193 is passed through line 197 to regeneration zone 198. Another portion of the hydrogen fluoride is passed through line 194 containing heater 195 through line 196 to hydrogen fluoride regeneration zone 198. The hydrogen uoride is purified in this regeneration zone by fractionation. This fractionation zone is conveniently a tower two and one-half feet in diameter, containing six trays eighteen inches apart. It is operated at 85 p. s. i. g. with a top temperature of 270 F. and a bottom temperature of 330 F. The regenerated hydrogen fluoride from zone 198 s passed through line 199, condensed in condenser 200, and passed via lines 201 and 188 to hydrogen uoride charge drum 189 for recirculation to the process as hereinabove described. Heavy tar-like polymers in an amount of about barrels per day are withdrawn from hydrogen fluoride regeneration zone 198 through line 202 for disposal.

Another specific example of the operation of the process with concentrated sulfuric acid as the alkylation catalyst and as the process is carried out similar to that set forth hereinabove with reference to Figure I is described herewith noW in connection with Figure III.

This example again illustrates the alkylation of isobutane with C4 oleiins. The isobutane is obtained by precise fractionation of eld butanes. The C4 olens are obtained from a uid catalytic cracking unit gas concentration plant and consist of the debutanzer overhead from this plant. Reaction conditions include 45 F. in the contacting zone, an isobutane to oleln mol ratio of 6.0:1, and an isobutane content greater than 50 mol percent in the contacting zone euent.

Referring to Figure III, an isobutane-n-butane stream comprising field butanes in the quantity of 1058 barrels per day, passed as a liquid under pressure through line 201, and is pumped by charge pump 202 to lines 203 and 204 to an upper portion of feed desobutanizer 205. These eld butanes have a composition as follows: 1.0 mol percent propane, 45.0 mol percent isobutane, and 54.0 mol percent n-butane. The feed desobutanizer is a fractionation tower with an inside diameter of four and onehalf feet, a height of one hundred and thirty feet, containing 60 trays spaced 24 inches apart. This fractionation zone operates at p. s. i. g. with the top temperature of 138 F., a bottom temperature of 160 F., and a 35:1 reflux ratio. The above-described butane stream has combined therewith in line 204, 587 barrels per day of recycle isobutane-lean n-butane from line 281 as hereinafter described. This recycle isobutane-lean n-butane stream consisting of the debutanzer overhead contains 25.9 mol percent isobutane, 73.5 mol percent n-butane, and 0.67 mol percent pentanes. Thus the total combined feed to desobutanizer 205 amounts to 1645 barrels per day and has a composition as follows: 0.6 mol percent propane, 38.2 mol percent isobutane, 61.0 mol percent n-butane, and 0.2 mol percent pentanes. The combined feed to desobutanizer 205 is fractionated therein under reux as hereinabove set forth and a substantially n-butane free isobutane is separated overhead therefrom in an amount of 629 barrels per day. This 629 barrels per day containing 1.7 mol percent propane. 93.3 mol percent isobutane, and 5.0 mol percent n-butane, is withdrawn from desobutanizer 205 overhead through line 206 and is condensed in condenser 207 and passes through line 208 to desobutanizer receiver 209. The liquid is withdrawn from the receiver through line 210, is pumped by pump 211 through line 212 to reflux line 213 and depropanizer feed line 214.

An olefin-containing stream from gas concentration debutanzer overhead (comprising low boiling hydrocarbons produced by a fluid catalytic cracking unit) is passed as a liquid under pressure through line 215 and pumped by pump 216 through line 217, condenser 218 and line 219 to depropanizer 220. This olefin-containing stream has a composition as follows: 0.4 mol percent ethane, 22.5 mol percent propylene, 16.4 mol percent propane, 29.1 mol percent butenes, 16.7 mol percent isobutane, 14.2 mol percent n-butane, 0.3 mol percent pentenes, and 0.4 mol percent pentanes; and is fed to the depropanizer in the quantity of 2849 barrels per day. It is joined in line 217 with 673 barrels per day of isobutane drag stream from line 263 consisting of 3.0 mol percent propane, 76.6 mol percent isobutane, 19.2 mol percent nbutane, 0.5 mol percent pentanes, and 0.7 mol percent light alkylate. The depropanizer .serves two functions. By recycle of butane drag stream through line 263 to the depropanizer, the propane made during hydrogen transfer reactions in the alkylation process is removed from the process and propane buildup therein is thus prevented. Also, the depropanizer serves as a feed preparation fractionation zone for separating C3 hydrocarbons and higher boiling hydrocarbons which C3 hydrocarbons can be sent to a polymerization unit for the preparation of motor fuel blending components therefrom. Depropanizer 220 is a fractionation column four and one-half feet in diameter, seventy feet high containing 30 trays spaced 24 inches apart. It operates at 275 p. s. i. g. with a top temperature of 125 F., a bottom temperature of 220 F., and a reux to feed ratio of 1.21:1. The total combined depropanizer feed from line 214 as hereinabove described in the quantity of 629 barrels per day, from line 215 in the quantity of 2849 barrels per day, and from line 263 in the quantity of 673 barrels per day has a composition as follows: 0.3 mol percent ethane, 15.7 mol percent propylene, 12.3 mol percent propane, 20.6 mol percent butenes, 36.6 mol percent isobutane, 13.7 mol percent n-butane, 0.3 mol percent pentanes, and 0.1 mol percent light alkylate. After fractionation of Ithe combined feed, the depropanizer overhead is passed through line 221, condenser 222, and line 223 to depropanzer receiver 224. The liquid hydrocarbons are withdrawn therefrom in line 225 by pump 226 which discharges into line 227 for reux through line 228 and net depropanizer overhead withdrawal of 1017 barrels per day is through line 229. The net depropanizer overhead withdrawal through line 229 in the quantity of 1017 barrels per day has a composition as follows: 0.1 mol percent ethane, 55.2 mol percent propylene, 42.4 mol percent propane, 0.4 mol percent butenes, 0.7 mol percent isobutane, and 0.20 mol percent n-butane. As hereinabove stated this depropanizer overhead stream is a suitable feed stock for catalytic polymerization for the production of high antiknock motor fuel blending components.

The depropanizer is heated by reboiling a portion of the higher boiling hydrocarbons which are withdrawn from the bottom of the depropanizer through line 230 to reboiler 231. The heated heavier hydrocarbons are then passed back through line 232 to the bottom of the depropanizer wherein heat is imparted to the depropanizer. The heav ier hydrocarbons comprising the net contactor feed are withdrawn from the depropanizer through line 233, cooled in condenser 234, and passed through lines 235, 236 and 237 to heat exchanger 238 for heat exchange with the contactor effluent. This net feed in the amount of 3,134 bbl./day has a composition as follows: 0.3 mol percent propylene, 0.6 mol percent propane, 28.5 mol percent butenes, 50.5 mol percent isobutane, 18.9 mol percent nbutane, 0.4 mol percent pentenes, 0.5 mol percent pentanes, and 0.2 mol percent light alkylate. This net contactor feed is combined in line 236 with recycle isobutane from the isostripper hereinafter described, said recycle isobutane being passed to line 236 via line 267. This recycle isobutane is supplied in the quantity of 5,255 barrels/ day and has a composition as follows: 3.0 mol percent pro pane, 76.7 mol percent isobutane, 19.1 mol percent nbutane, 0.5 mol percent pentanes and 0.7 mol percent light alkylate. The combination of the recycle isobutane from line 267 with the depropanizer bottoms from line 235 results in a combined contactor feed of 8,389 barrels per day having a combined composition as follows: 0.1 mol percent propylenc, 2.1 mol percent propane, 10.8 mol percent butenes, 66.6 mol percent isobutanes, 19.0 mol percent n-butane, 0.2 mol percent pentenes, 0.5 mol percent pentanes and 0.5 mol percent light alkylate. Recycle and fresh acid joins this combined feed stream from line 298 at line 237 and passes therewith to contactor 240. Contactor 240, containing liquid concentrated sulfuric acid, is maintained at 45 F. and alkylation of isobutanes in the combined feed stream with the butenes also contained therein takes place. As is Well known to one skilled in the art, sulfuric acid catalyzed alkylation of an isoparain with an olefin must be carried out at relatively low temperature. Thus, contactor 240 will contain refrigeration means not shown. Similarly, this alkylation must be carried out under emulsiiied phase conditions and thus efficient contacting within the contactor must be accomplished. This efiicient contacting and emulsication is accomplished by continually passing a portion of the reaction mixture from contactor 240 through line 241 to recycle pump 242. The action of the pump results in emulsification and mixing, and the reaction mixture is then returned to contactor 240 from pump 242 via line 243.

The mixture of hydrocarbons and acid catalyst carried over therewith is then withdrawn from contactor 240 through line 244, heat exchanged with the fresh combined feed in heat exchanger 238, and passed to alkylation settler 246 via line 245. The total effluent from contactor 240 amounts to 8,077 barrels per day and has a composition as follows: 2.6 mol percent propane, 62.0 mol percent isobutane, 21.4 mol percent n-butane, 1.3 mol percent pentanes, 12.2 mol percent light alkylate, and 0.4 mol percent heavy alkylate.

The hydrocarbon efuent, as described hereinabove, containing dissolved and emulsied sulfuric acid is withdrawn from settler 246 through line 247 and passed to caustic wash zone 248. Dilute caustic, such as 10% sodium hydroxide, is introduced to caustic wash zone 248 from means not shown through line 249 and is withdrawn therefrom via line 250. The caustic washed net contactor effluent is withdrawn from caustic wash zone 248 via line 251, which is connected with water wash zone 252. The hydrocarbons are washed wtih Water introduced to water wash zone 252 through line 253 for removal of traces of caustic, and the water wash is withdrawn through line 254. The caustic washed and water washed net contactor effluent is then passed from water wash zone 252 via line 255 and is introduced to isostripper 256. This introduction is made to the top tray of the isostripper. The isostripper is a fractionation column 5 feet in diameter and feet high containing 40 trays spaced 24 inches apart. It operates at a pressure of p. s. i. g. with a top temperature of 150 F., and a bottom temperature of 265 F. It operates without external reflux. Within this isostripper 256 a substantial separation is made between the lower boiling isobutane and the higher boiling normal butane and reaction products. The isostripper overhead is withdrawn through line 257, cooled in condenser 258, and passes through line 259 to the isostripper overhead receiver 260. This isostripper overhead stream in the amount of 5,928 barrels/ day has a composition as follows: 3.0 mol percent propane, 76.7 mol percent isobutane, 19.1 mol percent n-butane, 0.5 mol percent pentanes and 0.7 mol percent light alkylate. Prom the isostripper overhead receiver is withdrawn 5,255 barrels/day of net recycle through line 265 by pump 266 which discharges to line 267 and to 236 as hereinbefore described. The composition of this net recycle stream is set forth hereinabove. A drag stream comprising 673 barrels/ day is Withdrawn from isostripper overhead receiver 260 for propane removal from the system. This drag stream, which has the same composition as the recycle stream, is withdrawn from isostripper overhead receiver 260 through line 261 by pump 262 which discharges into lines 263 and 217 as hereinabove set forth.

The isostripper is heated by reboiling a portion of the higher boiling hydrocarbons which are withdrawn from the bottom of the isostripper through line 268 to reboiler 269. The heated heavier hydrocarbons are passed through line 270 back to the bottom of the isostripper wherein heat is imparted to said isostripper. The heavier hydrocarbons containing some isobutane which has not been removed overhead, n-butane and the reaction products are withdrawn through line 271 to debutanizer 272. This isostripper bottoms stream amounts to 2,149 barrels/day and has a composition as follows: 9.5 mol percent isobutane, 30.2 mol percent n-butane, 4.3 mol percent pentanes, 54.4 mol percent light alkylate, and 1.7 mol percent heavy alkylate.

The debutanizer is a fractionation zone 3 feet in diameter, 70 feet high, containing 30 trays spaced 24 inches apart. It is operated at 90 p. s. i. g. with an overhead temperature of F. and a bottoms temperature of 330 F. using a reux to feed ratio of 0.75 to 1. The overhead from debutanizer 272 passes through line 273, is condensed in condenser 274 and passes through line 275 to debutanizer overhead receiver 276. The liquid hydrocarbon debutanizer overhead is withdrawn from 15 debutanizer overhead receiver 276 through line 277 by pump 278 which discharges into line 279 connected to line 280 for reflux and line 281 for recycle of the net overhead to the feed deisobutanizer via line 281 as hereinbefore described. The net debutanizer overhead in an amount of 587 barrels per day has the following composition: 25.9 mol percent isobutane, 73.5 mol percent nbutane and 0.7 mol percent pentanes. By means of this recycle, isobutane loss from the system is minimized or prevented. The debutanizer is heated by reboiling a portion of the -high boiling hydrocarbons which are withdrawn from the bottom of the debutanizer through line 282 to reboiler 283. The heated heavier hydrocarbons are then passed through line 284 back to the bottom of debutanizer 272 wherein heat is imparted to said debutanizer. The net alkylate product is withdrawn from the bottom of the debutanizer through line 285, containing cooler 286 and is passed through line 287 to further fractionation means not shown. This net alkylate stream is in the amount of 1,562 barrels/day and has a composition as follows: 5.0 mol percent n-butane, 6.5 mol percent pentanes, 86.0 mol percent light alkylate, and 2.7 mol percent heavy alkylate. The F-l clear octane number of the light alkylate produced is 93.0-94.0.

As hereina-bove set forth, the debutanizer overhead is recycled to the feed preparation deisobutanizer for recovery of isobutane. This feed deisobutanizer 205 is heated by reboiling a portion of the higher boiling hydrocarbons, namely, n-butane, which is withdrawn from the bottom of the deisobutanizer through line 288 to reboiler 289. The heated higher boiling hydrocarbons are then passed through line 290 back to the bottom of the deisobutanizer 205 wherein heat is imparted to said deisobutanizer. The higher boiling hydrocarbon, namely, n-butane, s withdrawn from the deisobutanizer through line 291, cooled in condenser 292, and withdrawn from the system through line 293. This stream amounts to 1,016 barrels/day and has a composition as follows: 5.0 mol percent isobutane, 94.7 mol percent n-butane, and 0.3 mol percent pentanes. This stream is conveniently utilized for motor fuel blending to obtain desired vapor pressure or, if desired, may be passed to an isomerization process wherein the n-butane is converted to isobutane for reuse in the alkylation process.

Sulfuric acid is continuously replaced in an alkylation process. As hereinabove set forth, sulfuric acid dissolved in or carried over with the hydrocarbon effluent from contactor 240 is settled therefrom as a lower layer in settler 246. This lower layer of sulfuric acid is conveniently recycled within the process by withdrawal thereof from settler 246 through lines 294, 295 and 296 connected to pump 297 which discharges the recycle sulfuric acid to lines 298 and 237 as aforesaid. Since about 0.6 pound of sulfuric acid are consumed per gallon of alkylate produced, it is necessary to withdraw this amount of spent catalyst from the system and to introduce fresh sulfuric acid in its place. Withdrawal of spent sulfuric acid is accomplished by passing 39,400 pounds of sulfuric acid per day from settler 246 through lines 294 and 299 for disposal. Fresh concentrated sulfuric acid in a like amount is continually introduced through line 300 to line 296 where it is continuously circulated to the contactor by pump 297 discharging into lines 298, 237 and 239. The spent sulfuric acid is disposed of by neutralization or by other methods well known to one skilled in the art of refinery operations.

I claim as my invention:

l. An improved process for producing a high antiknock hydrocarbon fraction by reacting an isoparain and an olefin in the presence of a hydrogen uoride alkylation catalyst which comprises fractionating a mixed n-parain isoparafn stream and an isoparain-lean parafiin stream produced as hereinafter described in a fractionation zone to produce a substantially n-paran-free isoparain overhead fraction and a substantially isos paraffin-free n-parain bottoms fraction, contacting said isoparaflin fraction with an isoparafn-rich parain recycle fraction produced as hereinafter described and an olefin in the reaction zone in liquid phase in the presence of a hydrogen uoride alkylation catalyst, separating from effluents of said reaction zone a liquid phase cornprising primarily hydrogen fluoride alkylation catalyst and a liquid hydrocarbon phase containing dissolved hydrogen fluoride and comprising a large excess of unreacted isoparaflin, n-parafn, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating therefrom an isoparain-rich paraffin fraction overhead containing said dissolved hydrogen uoride, recycling said isoparain-rich paraffin fraction to the reaction zone, separating an isoparain-lean n-parain and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating a low boiling isoparain-lean paraffin fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isoparain-lean parain fraction to said first-mentioned fractionation zone for recovery of isoparain therefrom.

2. An improved process for producing a high antiknock hydrocarobn fraction by reacting isobutane and an olefin in the presence of a hydrogen uoride alkylation catalyst which comprises fractionating a mixed n-bntane isobutane stream and an isobutane-lean n-butane stream produced as hereinafter described in a fractionation zone to produce a substantially n-butane-free isobutane overhead fraction and a substantially isobutane-free n-butane bottoms fraction, contacting said isobutane fraction with an isobutane-rich paraffin recycle fraction produced as hereinafter described and an olefin in a reaction zone in liquid phase in the presence of a hydrogen uoride alkylation catalyst, separating from eiuents of said reaction zone a liquid phase comprising primarily hydrogen fluoride alkylation catalyst and a liquid hydrocarbon phase containing dissolved hydrogen fluoride and comprising a large excess of unreacted isobutane, n-butane, and resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating therefrom an isobutane-rich paraffin fraction overhead containing said dissolved hydrogen uoride, recycling said isobutane-rich parain fraction to the reaction zone, separating an isobutane-lean n-butane and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating a low boiling isobutane-lean n-butane fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isobutane-lean n-butane fraction to said first-mentioned fractionation zone for recovery of isoparain therefrom.

3. An improved process for producing a high antiknock hydrocarbon fraction by reacting isobutane and a butene in the presence of a hydrogen uoride alkylation catalyst which comprises fractionating a mixed n-butane isobutane stream and an isobutane-lean n-butane stream produced as hereinafter described in a fractionation zone to produce a substantially n-butane-free isobutane overhead fraction and a substantially isobutane-free n-butane bottoms fraction, contacting said isobutane fraction with an isobutane-rich parain recycle fraction produced as hereinafter described and a butene in a reaction zone in liquid phase in the presence of a hydrogen fluoride alkylation catalyst, separating from efliuents of said reaction zone a liquid phase comprising primarily hydrogen uoride alkylation catalyst and a liquid hydrocarbon phase containing `dissolved hydrogen fluoride and comprising a large excess of unreacted isobutane, n-butane, and the resulting higher boiling hydrocarbons, passing said liquid hydrocarbon phase directly to the top section of a stripping means, separating therefrom an isobutane-rich paraf- 17 n fraction overhead containing said dissolved hydrogen uoride, recycling said isobutane-rich parain fraction to the reaction zone, separating an isobutane-lean n-butane and higher boiling hydrocarbon stream from the bottom of said stripping means, passing said last-mentioned stream to a fractionation zone, separating a low-boiling iso-butane-lean n-butane fraction overhead therefrom and a high antiknock stream from the bottom thereof, and recycling the overhead isobutane-lean n-butane fraction to said first-mentioned fractionation zone for recovery of isobutane therefrom.

References Cited in the ile of this patent UNITED STATES PATENTS 

1. AN IMPROVED PROCESS FOR PRODUCING A HIGH ANTIKNOCK HYDROCARBON FRACTION BY REACTION AN ISOPARAFFIN AND AN OLEFIN IN THE PRESENCE OF A HYDROGEN FLUORIDE ALKYLATION CATALYST WHICH COMPRISES FRACTIONATING A MIXED N-PARAFFIN ISOPARAFFIN STREAM AND AN ISOPARAFFIN-LEAN PARAFFIN STREAM PRODUCED AS HEREINAFTER DESCRIBED IN A FRACTIONATION ZONE TO PRODUCE A SUBSTANTIALLY N-PARAFFIN-FREE ISOPARAFFIN OVERHEAD FRACTION AND A SUBSTANTIALLY ISOPARAFFIN-FREE N-PARAFFIN BOTTOMS FRACTION, CONTACTING SAID ISOPARAFFIN FRACTION WITH AN ISOPARAFFIN-RICH PARAFFIN RECYCLE FRACTION PRODUCED AS HEREINAFTER DESCRIBED AND AN OLEFIN IN THE REACTION ZONE IN LIQUID PHASE IN THE PRESENCE OF A HYDROGEN FLUORIDE ALKYLATION CATALYST, SEPARATING FROM EFFLUENTS OF SAID REACTION ZONE A LIQUID PHASE COMPRISING PRIMARILY HYDROGEN FLUORIDE ALKYLATION CATALYST AND A LIQUID HYDROCARBON PHASE CONTAINING DISSOLVED HYDROGEN FLUORIDE AND COMPRISING A LARGE EXCESS OF UNREACTED ISOPARAFFIN, N-PARAFFIN, AND RESULTING HIGHER BOILING HYDROCARBONS, PASSING SAID LIQUID HYDROCARBON PHASE DIRECTLY TO THE TOP SECTION OF A STRIPPING MEANS, SEPARATING THEREFROM AN ISOPARAFFIN-RICH PARAFFIN FRACTION OVER- 